A Terrain Awareness and Warning System (TAWS) is a system designed to alert pilots if their aircraft is in danger of making contact with a terrain feature. The terrain feature, by way of example, may be mountainous terrain, water terrain, or even a manmade structure.
One type of TAWS is an Enhanced Ground Proximity Warning System (EGPWS) that utilizes a digital terrain database stored in a computer memory on the aircraft. The EGPWS utilizes on-board computers in conjunction with long-range navigation systems such as global positioning systems (GPS), inertial navigation systems (INS), radio-dependent navigational systems, or some combination of the above, to periodically compare the aircraft's position relative to information in the digital terrain database.
One drawback of these systems is that the information in the digital terrain database may not recognize all possible or potential landing sites throughout the world. In such a situation, the aircraft may have occasion to land, either in intentionally or during an emergency, in areas that are not identified in the database. During intentional landings into unknown airports, for example, the current systems continuously and repeatedly broadcast at least some of the visual/audio alerts even though the aircraft has been intentionally placed into a proper landing configuration. Thus, a need exists for handling the alerts from the EGPWS when landing an aircraft at an unknown or unrecognized airport.